I have a 1989 jeep grand cherokee, I bought a new Kenwood Stereo KDC - MP342U, I am having a problem powering the unit on. I purchased a wiring harness for the stereo and hooked it up wire for wire. When I powered on the unit it went into a protect mode. There also is a black wire that needs to be attached to the chassis, when this done my clock powers off, what could be causing this error.